Numerous methods have been disclosed to characterize and treat crude oils or refinery feedstocks. Crude oil feedstocks typically contain organic acids such as carboxylic or naphthenic or mineral acids such as hydrochloric, phosphoric, hydrogen sulfide and various oxidized forms of hydrogen sulfide such as sulfuric acid. Evaluation of corrosivity of refinery feedstocks has typically been done by measuring the Total Acid Number (TAN). TAN is computed based on milligrams of KOH required to neutralize one gram sample of the crude.
U.S. Pat. No. 6,294,387 discloses a method for determining corrosiveness of crude oil containing naphthenic acid by measuring the iron content in the crude oil, so as to provide a measure of the extent of corrosion from the naphthenic acids over a period of time.
There is still a need for improved methods to evaluate the corrosivity of crude oil feedstocks, particularly under harsh operating conditions of high temperatures where the iron content in the oil is an unreliable measure of the extent of corrosion. There is also a need to characterize crude oil feedstocks by their corrosivity characteristics.